Purrlock, by Jenny Parks. I like that she's chosen an elegant Oriental-type for Sherlock, while John is your ordinary tabby cat. So appropriate, both of them. (Edited to add - looking at the colour of John's eyes, I reckon he's a British Shorthair!)

She does cats as a lot of different TV and movie characters, and you can see her gallery here. Also some of her science illustrations. So very talented - I can't draw stick people so I greatly admire anyone who can draw or paint.